1. Field of the Invention
The present invention relates to a method and appratus for sterilizing water (water to be treated) (hereinafter, “water to be treated” will be referred to as “for-treatment water”) such as water used for drinking and cooking or waste water discharged from hydroponics or a fish hatchery and to a hydroponics system using the apparatus.
2. Description of the Related Art
Heretofore, for example, to remove microorganisms such as bacteria, fungi and protozoans contained in water intended for drinking and cooking such as tap water reserved in a reservoir, a method has been employed in which a porous filter material capable of collecting these microorganisms is placed in a water channel so as to make the microorganisms stick to the filter material and thereby purify the water.
Further, in addition to this, there is also a method in which chlorine and ozone are produced in accordance with electrolysis caused by electrodes immersed in water intended for drinking and cooking and microorganisms contained in the water are eliminated by sterilizing effects of produced chlorine and ozone.
Meanwhile, in hydroponics, a solution prepared by dissolving a fertilizer in water in an amount suitable for cultivation of crops is circulated through a cultivation bed so as to suitably grow crops planted in the cultivation bed. However, the inside of the cultivation bed through which the fertilizer solution is circulated is an environment suitable for proliferation of pathogenic bacteria such as Fusarium (a type of fungi), and if the Fusariums are proliferated in the cultivation bed, they damage roots of the crops and cause the crops to die. Under the circumstances, it has been practiced that the fertilizer solution is heated by means of a heater and that an apparatus which is installed in a translucent jacket and has a structure that pathogenic bacteria contained in the fertilizer solution are killed by ultraviolet radiation or ozone is disposed in a path through which the fertilizer solution is circulated.
Meanwhile, such a filter material collects microorganisms by catching them in fine pores formed on its surface. Therefore, it cannot collect the microorganisms unless they collide against or pass near the surface of the filter material. Consequently, its effect of collecting the microorganisms is limited.
Further, since the microorganisms stick to the filter-material as described above, the filter material eventually becomes saturated and releases the microorganisms in the water channel. Under the circumstances, it is conceivable to heat the filter material so as to kill the stuck microorganisms. However, some microorganisms are resistant to heat, and to ensure a sterilizing effect, the filter material must be heated to a relatively high temperature.
In addition, although the fertilizer solution in the hydroponics is heated so as to kill the pathogenic bacteria proliferated in the cultivation bed, the plants die when the heated fertilizer solution is used as it is. Thus, a cooling device for cooling the heated fertilizer solution is also required. For this reason, there is a problem that a large amount of energy must be consumed so as to heat and cool the fertilizer solution. Further, there is another problem that when the pathogenic bacteria contained in the fertilizer solution are killed by use of ultraviolet radiation or ozone, concentrations of iron and manganese contained in the fertilizer solution are reduced.
The present invention has been conceived to solve the above technical problems of the prior art. An object of the present invention is to provide a water treating method and water treating apparatus which can significantly improve an effect of eliminating microorganisms contained in water intended for drinking and cooking or waster water and a hydroponics system using the apparatus.